1. Field of the Invention
This invention relates to the homopolymerization inhibition of bis(vinylsulfonyl)alkane hardeners. In one aspect, the invention relates to compositions comprising a hydrophilic colloid, a bis(vinylsulfonyl)alkane hardener and an inhibitor for homopolymerization of the hardener. In another aspect, the invention relates to methods for inhibiting homopolymerization of bis(vinylsulfonyl)alkane hardeners in preparing photographic elements. In still another aspect, the invention relates to photographic elements hardened with a composition comprising a homopolymerization inhibited bis(vinylsulfonyl)alkane hardener.
2. Description of the State of the Art
In the photographic arts hydrophilic colloids, typically refined gelatin, have been used in photographic elements to form layers, such as radiation-sensitive layers (e.g., silver halide emulsion layers), interlayers, subbing layers and overcoat layers. Various addenda are conventionally incorporated in the layers, including addenda to alter the properties of the hydrophilic colloids present. It has been recognized previously in the art that without special modifiers hydrophilic colloids such as gelatin are easily abraded and ingest large quantities of water when brought into contact with aqueous solutions, thereby causing an undesirable amount of swelling. Also, unmodified colloid coatings tend to melt at relatively low temperatures, thereby limiting their temperature range of utility. To obviate these deficiencies certain addenda generically designated as "hardeners" are incorporated into hydrophilic colloids intended to be used in forming photographic element layers. Both inorganic and organic hardeners are known. A summary of hardeners is presented by T. H. James, The Theory of the Photographic Process, 4th Ed., MacMillan, 1977, pp. 77-87. The terms "forehardened" and "forehardener" are employed when the hardener is associated with hydrophilic colloid in the course of manufacturing a photographic element. The terms "prehardened" and "prehardener" are employed when the hardener is associated with a hydrophilic colloid layer of a photographic element in a processing solution preceding the developer bath for the element.
Among hardeners of the active olefin type, a preferred class of hardeners particularly useful as forehardeners are bis(vinylsulfonyl)alkane hardeners. Bis(vinylsulfonyl)alkane hardeners are believed to be effective as hardeners as a result of their ability to crosslink polymers making up the colloid. One disadvantage that has been observed in using bis(vinylsulfonyl)alkane hardeners is that these hardeners, particularly the more active ones, will homopolymerize. Homopolymerization can occur before the hardeners are associated with the hydrophilic colloid and it can occur as a competing reaction after association. The tendency of the hardeners to homopolymerize is disadvantageous in requiring careful selection of hardener preparation and handling conditions and in causing hardener to become unavailable for the desired crosslinking reaction with the hydrophilic colloid.
Polymerization inhibitors are known in the art. Frank and Adams, "The Relative Efficiency of Some Polymerization Inhibitors", Journal of the American Chemical Society (JACS), Vol. 68, 1946, p. 908, lists a number of polymerization inhibitors, including picric acid and trinitrobenzene, and reports their effects on styrene, 3,4-dichlorostyrene and 5-ethyl-2-vinylpyridine. Bartlett and Kwart, "Dilatomic Studies of the Behavior of Some Inhibitors and Retarders in the Polymerization of Liquid Vinyl Acetate", JACS, Vol. 72, 1950, pp. 1050-1059, discusses the polymerization inhibiting effectiveness of p-nitrotoluene, nitrobenzene, dinitrodurene and dinitrobenzene on inhibiting polymerization of vinyl acetate. J. Ulbricht, "Inhibitors and Inhibition Constants in Free Radical Polymerization", Polymer Handbook, 1966, pp. II-71-75, reports quantitatively inhibiting effects of a number of nitrobenzene and nitrobenzoic acid compounds on monomers, such as methyl acrylate, methyl methacrylate, vinyl acetate and styrene. The gross variations in the numbers reported by Ulbricht effectively refute the statement by Frank and Adams that a good inhibitor for one monomer is likely to be a good inhibitor for another. Margerum U.S. Pat. No. 3,556,794, issued Jan. 19, 1971, discloses in column 7, lines 20 through 60, for example, ultraviolet responsive desensitizers for photopolymers of the type described, for example, in column 9, lines 13 through 22. A variety of nitro-substituted benzoic acid and ester desensitizers are disclosed and a variety of vinyl monomers.
The use of nitro-substituted aromatic compounds, such as nitrobenzenes, nitrobenzoic acid, and the like, in photographic elements is known in the art. Pollett et al U.K. Pat. Nos. 1,399,449 and 1,399,450, disclose the use of nitro-substituted aromatic compounds to stabilize silver halide photographic elements against fog formation during high temperature processing (greater than 30.degree. C.). Edens U.S. Pat. No. 3,832,179, issued Aug. 27, 1974, discloses the use of nitrobenzoic acids to suppress fog formation in color photographic elements. Brown et al U.S. Pat. No. 2,415,624, issued Feb. 11, 1947, discloses incorporating dinitrobenzoic acid in an overcoat of a photographic element to act as a filter for ultraviolet light. None of these patents disclose the use of hardeners of the vinylsulfonyl type.
Since inhibition of homopolymerization of bis-(vinylsulfonyl)alkane hardeners must be achieved while not interfering with the ability of these hardeners to crosslink with the hydrophilic colloid, it is not surprising that among compounds investigated prior to this invention as homopolymerization inhibitors for photographic bis(vinylsulfonyl)alkane hardeners only hydroquinone has been identified as useful. Burness et al U.S. Pat. No. 3,841,872, issued Oct. 15, 1974, and corresponding U.S. Pat. No. Re. 29,305, reissued July 12, 1977, disclose examples wherein hydroquinone is employed in the preparation of bis(vinylsulfonyl)alkane hardeners. In addition to being limited in the homopolymerization inhibition effect obtained, particularly with the more active hardeners, hydroquinone also exhibits certain other disadvantageous properties, such as (1) formation of colored impurities and (2) formation of addition products which are inactive or insoluble.